1. Field of the Invention
The present invention relates generally to the field of lighting and, more particularly, to a replaceable lighting unit with adjustable output intensity (lumens) and optional capability for reporting usage information (e.g., time in use), and associated method of operation.
2. Description of Related Art
Light emitting diodes (LEDs) are highly efficient electrical light sources and are being utilized increasingly for indoor, outdoor and vehicular lighting purposes. Typically, several LEDs are incorporated into a lighting unit to produce a predetermined light output. The number and type of LEDs, as well as the design of the lens element that directs or concentrates the light produced thereby, determines the light output power and the power consumed by the lighting unit.
LEDs offer many advantages over incandescent, halogen and fluorescent lighting units. LEDs are highly shock resistant and, therefore, do not shatter when subjected to mechanical or thermal shock (e.g., when dropped). LEDs also possess operating life times that are substantially longer than their incandescent, halogen, and fluorescent counterparts. For example, in some cases, the operating life of an LED lighting unit may exceed 100,000 hours, as compared to the typical 1,000-2,000 hours for incandescent bulbs and 5,000-10,000 hours for fluorescent bulbs.
In certain applications, such as in large department stores, warehouses, and the like, a large number of lighting units are utilized to illuminate the space and/or to direct light to certain locations within the space. The low power consumption and extended useful life of LED lights makes them ideally suited for such lighting tasks.
Lighting units made with LEDs are more expensive than comparable incandescent, halogen or fluorescent bulbs, but consume far less power and last much longer. Although the low power consumption and extended life of LED lights make them the superior choice in lighting options, the initial capital outlay to install LED lights in large numbers is quite costly.
Moreover, in certain lighting arrangements, such as those used in department stores where displays are rearranged or reconfigured from time to time, users of the lighting arrangements may desire to vary the intensity of some or all of the lights in a given space. The high cost of LED lights may make the purchase of multiple, fixed intensity LED lights for each fixture impractical even though such lights are more energy efficient. Presently, there are no self-contained, adjustable intensity, replaceable lighting units available on the market, regardless of whether the light source is a set of LEDs or a more conventional incandescent, halogen, or fluorescent bulb. Rather, the intensity of a light bulb or a set of light bulbs in a light fixture may be controlled remotely through use of a specialized wall switch (e.g., a dimmer).
Additionally, LEDs operate at relatively high temperatures. Therefore, a heat dissipation structure, such as a heat sink, is typically employed to reduce the operating temperature of lighting units that employ LEDs. Lighting units employing LEDs sometimes realize temperatures that are so high that solder joints break or solder melts, causing previously soldered wires to be released and potentially exposed.
In addition, LED lighting units incorporate electronic components and circuit pathways, such as wires and printed circuit board traces. Standard certification bodies, such as Underwriters' Laboratories (UL), require that such components and circuitry be shielded and rendered inaccessible by a fire retardant material so as to avoid injury or fire. In many of today's electronic products, the materials housing the LED circuits are thermoplastics. To categorize the fire retardant capabilities of thermoplastic materials, UL and other certification companies establish fire rating certifications. For example, depending on a thermoplastic material's performance in UL's vertical burn test, UL classifies the material into one of five fire classes: UL 94, V0, V1, V2 or 5 V (or V5).
A thermoplastic material is classified in fire class UL 94 V0 if the following criteria are met: For a set of five samples measuring 127 mm×12.7 mm×3.16 mm, all samples can continue burning after application of a flame twice for 10 seconds. The sum of the combustion times after 10 flame applications to five samples must not be longer than 50 seconds. None of the samples must drip flaming particles, burn completely or burn with glowing combustion for longer than 30 seconds.
For classification in fire class UL 94 V1, the combustion times must not be longer than 30 seconds and the sum of the combustion times for 10 flame applications to five samples must not be longer than 250 seconds. Glowing combustion must never last longer than 60 seconds. The other criteria are identical to those mentioned above for fire class UL 94 V0. A material is classified in fire class UL 94 V2 when the above criteria for classification as UL 94 V1 are fulfilled and dripping of flaming particles occurs.
A plastic material is classified in fire class UL 94 V5 if the following criteria are met: The combustion time or glowing combustion time of the samples must not exceed 60 seconds after the final flame application. A flame 127 mm high and having an inner blue cone 38 mm high is applied to each sample five times for five seconds. Two successive flame applications are separated in each case by an interval of five seconds. Neither dripping of flaming or non-flaming particles nor complete combustion may occur.
When given, a UL 94-V5 rating indicates that the plastic materials used to house the lighting product have been tested in accordance with the UL vertical burn test criteria and have met the UL 94-V5 criteria based on a specified thickness of material. Thus, when a non-isolated power supply is used to supply power to the electrical components of the lighting device, a UL 94-V5 fire rating can only be achieved when the electrical wiring remains within a plastic enclosure that has a UL 94-V5 fire rating.
Further, due to the substantial operating lifetimes of LEDs, users of LED lighting units may not readily be able to anticipate when such lighting units will need to be replaced. For instance, the personnel in charge of maintaining the lighting units may turnover one or more times during the life of an LED lighting unit, potentially resulting in a loss of information regarding the amount of time the unit has been in use unless such personnel are precise in maintaining written use records. Such a loss of information may result in an unexpected reduction in intensity at an inopportune time. Additionally, turnover in personnel and the associated interruption in record-keeping may result in a loss of warranty and other usage information for each LED lighting unit.
Therefore, a need exists for a replaceable lighting unit that provides user-settable output intensity. Such a lighting unit that optionally shields electrical wiring to meet the UL 94-V5 fire rating and reports usage information would be a further improvement over the prior art.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated alone or relative to other elements to help improve the understanding of the various embodiments of the present invention.